Full duplex expander in a full duplex network

ABSTRACT

In one embodiment, a method receives a downstream signal and an upstream signal in a same frequency band. The downstream signal and the upstream signal are separated into a first path and a second path. The downstream signal using the first path and the upstream signal using the second path are amplified in an analog domain. The method isolates the downstream signal and the upstream signal from one another and sends the downstream signal downstream to a subscriber device and sends the upstream signal towards a full duplex node.

BACKGROUND

Full duplex communications, such as full duplex (FDX) Data Over CableService Interface Specification (DOCSIS), is a data delivery systemwhere both the downstream and the upstream traffic is delivered in thesame frequency band. For example, the downstream traffic may bedelivered from a head end to FDX nodes, which then deliver the trafficto subscriber devices located downstream. The upstream traffic isdelivered from subscriber devices through FDX nodes to the head end inthe same frequency band as the downstream traffic.

To deliver the full-duplex traffic, the network is converted to an N+0architecture, which means that the amplifiers in the network are removedand replaced with FDX nodes. The amplifiers are replaced because FDXtransmission is not compatible with the legacy analog amplifiers. Forexample, legacy analog amplifiers use diplex filters to provideisolation between the upstream amplification path and the downstreamamplification path. The diplex filters prevent the amplifier fromoscillating, but using the diplex filters only works because theupstream and downstream communications occur in different frequencybands. Thus, when upstream and downstream traffic is delivered in thesame frequency band, the legacy analog amplifiers cannot be used.

Converting the amplifiers to FDX nodes to use an N+0 architecture maysignificantly increase the cost and timeline required to roll out thenetwork to use full duplex transmission. The cost increases because theFDX nodes use fiber connections from the head end to the nodes and theamplifiers that are being replaced connected via coaxial cable and notconnected via fiber. A provider needs to replace the coaxial cable withfiber when the FDX node replaces the legacy analog amplifiers, which notonly increases the cost, but replacing the coaxial cable with fibertakes time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a simplified system for amplifying full duplex signalsaccording to some embodiments.

FIG. 2 depicts a more detailed example of the system according to someembodiments.

FIG. 3 depicts an example of a FDX regenerator according to someembodiments.

FIG. 4 depicts an example of a FDX repeater according to someembodiments.

FIG. 5A depicts an example of a FDX dual switched amplifier according tosome embodiments.

FIG. 5B depicts an example of a FDX bi-directional switched amplifieraccording to some embodiments.

FIG. 6 depicts a simplified flowchart of a method for processing fullduplex signals according to some embodiments.

FIG. 7 illustrates an example of a special purpose computer systemsconfigured with a FDX expander according to one embodiment.

DETAILED DESCRIPTION

Described herein are techniques for a full duplex communication system.In the following description, for purposes of explanation, numerousexamples and specific details are set forth in order to provide athorough understanding of some embodiments. Some embodiments as definedby the claims may include some or all of the features in these examplesalone or in combination with other features described below, and mayfurther include modifications and equivalents of the features andconcepts described herein.

Some embodiments provide a full duplex (FDX) expander that is used toamplify full duplex signals. The full duplex signals transmit bothupstream and downstream traffic in the same frequency band. The FDXexpanders can be used in place of analog amplification in the fullduplex network. The FDX expanders can receive a downstream signal and anupstream signal in the same frequency band where the downstream signalis received from a full duplex (FDX) node and the upstream signaloriginated from a subscriber device. The FDX expander then separates thedownstream signal and the upstream signal into separate paths. Thedownstream signal is amplified using a first path and the upstreamsignal is amplified using a second path. In some embodiments, the FDXexpander isolates the downstream signal and the upstream signal.Different methods for isolating the downstream signal and the upstreamsignal from one another are appreciated and will be described in moredetail below. After amplification, the FDX expander sends the downstreamsignal downstream toward a subscriber device and sends the upstreamsignal towards the FDX node. The FDX expander allows amplification to beperformed in the full duplex network without having to replace theamplifier with a FDX node. For example, the analog connection, such asvia a coaxial cable connection, to the FDX expander from the FDX nodecan be maintained in the full duplex system while continuing to provideamplification.

System Overview

FIG. 1 depicts a simplified system 100 of a method for amplifying fullduplex signals according to some embodiments. System 100 includes a FDXnode 102, an expander 104, and subscribers 110. It will be understoodthat other components of the network may be included, such as other FDXnodes 102 and expanders 104 may be included. Further, although notshown, a head end may be located upstream of FDX node 102. In someembodiments, FDX node 102 may be part of a remote physical (PHY) devicethat can be located closer to the subscriber's premises, such as in anode located in the neighborhood where the subscribers are located. Therelocated physical device is referred to as a remote physical device(RPD). FDX node 102 converts packets on a digital interface, such as anEthernet interface received via a digital network, such as via opticalfiber, to analog signals, such as radio frequency (RF) signals, on ahybrid fiber coaxial (HFC) network. FDX node 102 sends the RF signals tomodems located at a subscriber's premises via an analog network, such asvia coaxial cable.

Full duplex signals may include different types of traffic, such as dataand video. In the downstream direction, signals from the head end aresent through FDX node 102 toward subscribers 110 through expander 104. Agroup of subscribers may be connected to a tap 112 that providesconnections to subscribers 110. Subscribers 110 may include subscriberdevices, such as modems that receive the downstream signals and send theupstream signals. In some embodiments, the modems include cable modems,but other devices may be appreciated, such as gateways. In the upstreamdirection, subscribers 110 send upstream signals toward the head endthrough expander 104 and FDX node 102.

In the downstream direction, FDX node 102 may receive a downstreamsignal from the headend and process the downstream signal using fullduplex logic 106. As discussed above, FDX node 102 may receive packetsvia a digital network. Then, FDX node 102 sends the downstream signal toexpander 104. The downstream signal is sent via an analog network.Expander 104 then amplifies the downstream signal in the analog domain.Also, in the upstream direction, expander 104 receives upstream signalsand can amplify the upstream signals in the analog domain. Then,expander 104 sends the upstream signals towards the head end, whicheventually reach FDX node 102. The upstream signals are sent via theanalog network.

Expander 104 receives the downstream and the upstream signals in thesame frequency band, which may be a range of frequencies that includesboth the downstream and the upstream signals. In some embodiments, thedownstream and upstream signals are sent at the same time, but in otherembodiments may be sent at different times. Expander 104 may process thedownstream and upstream signals using isolation and amplification logic108, which may separate the downstream and upstream signals that aresent in the same frequency band. Isolation and amplification logic 108then can amplify the downstream signal using a first path and theupstream signal using a second path. The amplification is performed inthe analog domain while isolating the downstream signal and the upstreamsignal from one another. After amplification, expander 104 may send thedownstream signals toward subscribers 110 and send the upstream signalstoward a head end.

In some embodiments, FDX expanders 104 may replace legacy analogamplifiers in the network. The use of FDX expanders 104 allows fullduplex traffic to be sent in the network without having to replace thelegacy analog amplifiers with FDX nodes 102. Also, the connectionbetween FDX node 102 and FDX expanders 104 may be transmit analogsignals, such as radio frequency (RF) signals, that may be communicatedover a coaxial cable instead of fiber. This means that the signals inthe downstream direction from FDX node 102 to FDX expanders 104 may bein the analog domain. If fiber was used, then the communications fromFDX node 102 to another FDX node may be in the digital domain, whichwould require the coaxial cable to be replaced between two FDX nodes 102as described in the Background.

FIG. 2 depicts a more detailed example of system 100 according to someembodiments. In the network, various taps 112-1 to 112-18 are includedthat couple signals to subscribers 110. Additionally, different types ofFDX expanders 104 may be included in various positions to provideamplification in the network at different points.

FDX node 102 uses full duplex logic 106 to convert digital signals toanalog signals in the downstream direction and convert analog signals todigital in the upstream direction. In the downstream direction, fullduplex logic 106 in FDX node 102 may include a digital-to-analogconverter (DAC) that converts the digital signal to analog. Ananti-aliasing filter 204 may attenuate the higher frequencies to preventaliasing components from being sampled. Then, an amplifier 206 amplifiesthe signal. A directional coupler 208 couples the analog downstreamsignal to tap 112-1.

In the upstream direction, directional coupler 208 receives the analogupstream signal and couples the signal to amplifier 210, which amplifiesthe upstream signal. Then, an analog-to-digital converter 212 convertsthe analog signal to digital. The digital upstream signal can then besent toward the head end. Although this full duplex logic is described,it will be understood that other variations of the full duplex circuitrymay be appreciated.

In some embodiments, expander 104 may be implemented using threedifferent types of expanders, such as a FDX regenerator 104-1, a FDXrepeater 104-2, and/or a FDX switched amplifier 104-3. Although thisconfiguration of expanders 104 is described, it will be understood thatFDX regenerator 104-1, FDX repeater 104-2, and FDX switched amplifier104-3 may be placed in different positions in the network and otherimplementations will be appreciated. For example, all threeimplementations do not need to be implemented in a network, such as onlyone or two of the implementations may be used.

In one path, FDX node 102 may be coupled to FDX repeater 104-2, which isthen coupled to FDX switched amplifier 104-3. A second path couples FDXnode 102 to FDX repeater 104-2 and a third path couples FDX node 102 toFDX regenerator 104-1. FDX repeater 104-2 and FDX regenerator 104-1 mayfurther be coupled to other FDX repeaters or regenerators or switchedamplifiers further downstream in the network.

FDX expanders 104 may be located at N+1, N+2, etc. positions in thenetwork. For example, FDX repeater 104-2 may be located at the N+1position of a network and FDX switched amplifier 104-3 may be located atthe N+2 position. The N+X notation, which X is a number, means that FDXrepeater 104-2 is performing a first level of amplification from FDXnode 102 and FDX switched amplifier 104-3 is performing a second levelof amplification from FDX node 102. The number X is the number of nodesin which the signal is amplified.

FDX regenerator 104-1, FDX repeater 104-2, and FDX switched amplifier104-3 provide amplification of downstream and upstream signals whileproviding isolation. FDX regenerator 104-1 and FDX repeater 104-2 canisolate the downstream and upstream signals and amplify the downstreamand upstream signals at the same time. However, FDX switched amplifier104-3 may amplify downstream and upstream signals that are sent in atime divisional duplex (TDD) manner. That is, at one time, subscribers110 may be in a transmit or receive mode. In contrast, it is possiblefor FDX regenerator 104-1 and FDX repeater 104-2 to process signalswhile subscribers were in both transmit and receive modes at the sametime. For example, a first subscriber may be receiving a downstreamtransmission and a second subscriber may be sending an upstreamtransmission during a same time period. The downstream and upstreamtransmissions are processed by FDX regenerator 104-1 or FDX repeater104-2 during the same time period.

In the network, interference groups result when a modem in the networkis transmitting, other modems see that transmission and perceive thetransmission as noise interference. The magnitude of the interferencevaries based on the transmit power of the modem and the isolationbetween each modem pair. For some modem pairs, this interference levelwill severely limit the downstream receive signal-to-noise ratio (SNR)of the victim modem (e.g., the modem receiving the interference). Inthis case, the modem pairs will be assigned to a same interference groupand will not be allowed to transmit and receive simultaneously. Since asingle modem may limit the receive SNR of many modems, all of thesemodems are assigned to the same interference group. Typically, theseinterference groups are located near each other and have relatively fewisolating network elements. In this example where the modems in theinterference group are limited to transmitting at different times, FDXswitched amplifier 104-3 may be used without losing any of the fullduplex functionality of the network. That is, FDX switched amplifier104-3 may never process full duplex traffic at the same time and thuscan be used without any negative limitations on full duplex trafficbeing received and sent in the upstream and downstream directions at thesame time.

In some examples, the analysis of the network may be used to determinewhich type of FDX expander is used. For example, FDX regenerators 104-1may be used in positions in the network that are coupled to a largenumber of subscribers 110. Also, FDX switched amplifiers 104-3 may beused when coupled to a small number of subscribers 110 that are limitedto TDD communications.

The following will now describe the different types of FDX expanders 104in more detail.

FDX Regenerator 104-1

FIG. 3 depicts an example of FDX regenerator 104-1 according to someembodiments. Although this configuration of FDX regenerator 104 isdescribed, it will be understood that variations of the logic describedmay be appreciated. In FDX regenerator 104-1, the upstream anddownstream paths may contain the same functional elements.

FDX regenerator 104-1 includes two interfaces referred to as a FDX modemfunction 300 and a FDX master function 301. FDX modem function 300performs a function that implements a modem. Also, FDX master function301 may perform a function that is performed by FDX node 102. The use ofFDX modem function 300 and FDX master function 301 provides a modeminterface on the network side interface of FDX regenerator 104-1 and FDXmaster function 301 provides an interface similar to what is included inFDX node 102 on the subscriber side interface.

FDX regenerator 104-1 includes a downstream path and an upstream path.In the downstream direction, a directional coupler 302 receives thedownstream signal and can couple the downstream signal into thedownstream path to an amplifier 304. Amplifier 302 amplifies the signalin the analog domain. Amplification will be described as being performedin both FDX modem function 300 and a FDX master function 301, but itwill be understood that amplification may only be performed in one ofFDX modem function 300 and FDX master function 301. For example,amplification may be performed only in the transmit side, such as in FDXmaster function 301 in the downstream direction and in FDX modemfunction 300 in the upstream direction.

After amplification, an analog-to-digital converter 306 converts theanalog signal to a digital signal. Then, a decoder/controller 308 maydecode the signal, which fully deconstructs the signal and thenreconstructs the signal. The deconstruction may generate individual codewords for the digital signal. Decoder/controller 308 convert from acodeword that represents the instantaneous power in time of the waveformthat is intended to be retransmitted, into the fundamental data contentthat is encoded within that waveform. There is an analog waveform thatis present at the input of ADC 306 that represents the power over timeof the composite signal that is being sent through the network. ADC 306measures that power at a series of specific time instants and reports aseries of codewords that are proportional to the instantaneous power intime samples. Decoder/controller 308 performs the additional step oftaking these samples and demodulating them into the baseband signal suchthat it yields the actual data content of the signal.

Decoder/controller 308 then re-modulated/re-encoded the data and thenfeeds the data into to a digital-to-analog converter (DAC) 310 as aseries of codewords that once again represent the instantaneous power intime as a series of codewords. The DAC 310 receives the codewords andturns the codewords into an analog waveform with a power that matchesthe codeword values. The analog to digital conversion and the digital toanalog conversion is used to isolate the network side interface and thesubscriber side interface. That is, the receiver side is isolated fromthe transmitter side in either the downstream path or the upstream path.

An anti-aliasing filter 312 may then attenuate the higher frequencies toprevent aliasing components from being sampled. An amplifier 314 canthen amplify the signal. A directional coupler 316 couples the signal inthe downstream direction towards subscribers 110.

In the upstream direction, directional coupler 316 may receive theupstream signal that originated from subscribers 110 and couple theupstream signal to an amplifier 318, which amplifies the signal. Ananalog-to-digital converter 320 then converts the analog signal todigital. Decoder/controller 308 can then decode the signal and thenencode the signal, which deconstructs the signal and reconstructs thesignal. A digital-to-analog converter 322 converts the digital signal toanalog. An anti-aliasing filter 324 receives the signal and attenuatesthe higher frequencies. An amplifier 326 can then amplify the signal.Directional coupler 302 can then couple the upstream signal in theupstream direction.

FDX regenerator 104-1 may also isolate the downstream path and theupstream path by cancelling crosstalk. For example, crosstalkcancellation logic 328 may cancel any crosstalk that occurs between thedownstream direction and the upstream direction, such as preventing atransmitter of FDX regenerator 104-1 from corrupting the signal presentat a receiver of FDX regenerator 104-1. Crosstalk occurs when thedownstream signal is being sent downstream through directional coupler316, but then some amount of the downstream signal is directed in theupstream direction through amplifier 318. Similarly, crosstalk occurswhen the upstream signal is being sent upstream through directionalcoupler 302, but then some amount of the upstream signal is directed inthe downstream direction through amplifier 304. Crosstalk logic 328 maycancel the small amount of the downstream signal that is sent in theupstream direction by creating an inverse of the signal to cancel thecrosstalk as a function of frequency and phase shift. Also, crosstalklogic 328 similarly cancels the upstream signal that is sent in thedownstream direction. Crosstalk logic 328 provides isolation between thedownstream signal and the upstream signal.

The crosstalk cancellation may be performed in the digital or analogdomain. That is, crosstalk logic 328 may perform the crosstalkcancellation after the analog signals are converted to digital signals,or perform the crosstalk cancellation before the analog signals areconverted to digital signals. In FDX regenerator 104-1, crosstalkcancellation is performed on both the input and output sides ofdecoder/controller 308 to prevent the transmitter of FDX regenerator104-1 from corrupting the signal present at the receiver of FDXregenerator 104-1. The cancellation on both sides is needed becausecrosstalk may occur on both sides of decoder/controller 308.

FDX Repeater 104-2

FIG. 4 depicts an example of FDX repeater 104-2 according to someembodiments. The upstream and downstream paths include the samefunctional elements in this example. One difference between FDX repeater104-2 and FDX regenerator 104-1 is that the digitized signal is notfully deconstructed and reconstructed in FDX repeater 104-2. Rather, thedigitized signal includes digital code words of the entire spectrum, notindividual code words as described with respect to FDX regenerator104-1. The digitized signal may be included in a raw spectrum in adigital format and represents the power of the entire spectrum.

Similar to FDX regenerator 104-1, FDX repeater 104-2 includes a networkside interface and a subscriber side interface shown as a FDX modemfunction 400 and a FDX master function 401, respectively. FDX repeater104-2 also includes a downstream path and an upstream path. In thedownstream direction, a directional coupler 402 receives the downstreamsignal and can couple the downstream signal into the downstream path toan amplifier 404. Amplifier 404 amplifies the signal in the analogdomain. It will be understood that amplification does not need to beperformed on both sides of the ADC and DAC conversion as described withrespect to FDX regenerator 104-1.

After amplification, an analog-to-digital converter 406 converts theanalog signal to digital. Then, the digital signal may be sent to adigital-to-analog converter (DAC) 408 to convert the digital signal toanalog. As with the FDX regenerator, the analog to digital conversionand the digital to analog conversion is used to isolate the network sideinterface and the subscriber side interface. That is, the receiver sideis isolated from the transmitter side in either the downstream path orthe upstream path.

An anti-aliasing filter 410 may then attenuate the higher frequencies toprevent aliasing components from being sampled. An amplifier 412 maythen amplify the signal in the analog domain. A directional coupler 414couples the signal in the downstream direction.

In the upstream direction, directional coupler 414 may receive theupstream signal and couple the upstream signal to an amplifier 416,which amplifies the signal in the analog domain. An analog-to-digitalconverter 418 then converts the analog signal to digital. Adigital-to-analog converter 420 converts the digital signal to analog.An anti-aliasing filter 422 receives the signal and attenuates thehigher frequencies. An amplifier 424 can then amplify the signal in theanalog domain. Directional coupler 402 couples the upstream signal inthe upstream direction.

FDX repeater 104-2 may also isolate the downstream path and the upstreampath by canceling crosstalk. For example, crosstalk cancellation logic426 may isolate the upstream path and the downstream path by cancelingcrosstalk. Crosstalk cancellation logic 426 may cancel the crosstalk inthe digitized signal between analog-to-digital converter 406 anddigital-to-analog 408 and between analog-to-digital converter 418 anddigital-to-analog converter 420. Crosstalk logic 426 may perform thecrosstalk cancellation on both the downstream path and the upstreampath. Crosstalk cancellation logic 426 may be similar to crosstalkcancellation logic 328 of FDX regenerator 104-1. The cancellationapproach is similar between Crosstalk cancellation logic 426 may besimilar to crosstalk cancellation logic 328, but does not have to beidentical. In some embodiments, FDX regenerator 104-1 has the supersetof options for how cancellation can be implemented. FDX repeater 104-2may have a subset of these options. In some embodiments, any form ofcancellation that provides adequate crosstalk suppression may be used.

In both FDX repeater 104-2 and FDX regenerator 104-1, cancellation canbe performed in the analog domain, the digital domain, or partially inthe analog domain in order to reduce the magnitude of the crosstalkrelative to the message signal and then further cancelation is performedin the digital domain.

FDX Switched Amplifier 104-3

FIGS. 5A and 5B depict different examples of FDX switched amplifiers104-3 according to some embodiments. FIG. 5A includes separate upstreamand downstream amplifiers and FIG. 5B includes a single amplifier thatis switched between two directions. FDX dual switched amplifier 104-3may operate in a time division duplex (TDD) mode. In this example, theupstream signal and the downstream signal are not processed at the sametime. Accordingly, FDX dual switched amplifier 104-3 may be placedtowards the end of a network and coupled to subscribers 110 that send orreceive signals that interfere with one another. In this example,subscribers 110 cannot transmit or receive at the same time and thus theTDD mode of FDX dual switched amplifier 104-3 is acceptable because theupstream and downstream signals are being sent using TDD.

FIG. 5A depicts an example of a FDX dual switched amplifier 104-3according to some embodiments. A modem/controller 512 may controlswitches 504 and 508 to couple the upstream signal to the upstream pathand the downstream signal to the downstream path. For example,modem/controller 512 controls switches 504 and 508 based on whethersubscribers 110 coupled to FDX dual switched amplifier 104-3 are in atransmit mode or a receive mode. Modem/controller 512 receives thedownstream signal and determines that the subscriber is in receive mode.When not receiving the downstream signal, modem/controller 512determines that the subscriber is in transmit mode. When a subscriber110 is set to receive a downstream signal in a time slot,modem/controller 512 controls switches 504 and 508 to couple thedownstream signal to amplifier 506. Similarly, when a time slot occurswhen a subscriber 110 is transmitting an upstream signal,modem/controller 512 controls switches 504 and 508 to couple theupstream signal to amplifier 510.

In the downstream direction, FDX dual switched amplifier 104-3 mayreceive a downstream signal at a directional coupler 502. Directionalcoupler 502 can then send the downstream signal to a switch 504, such asa radio frequency (RF) switch. Modem/controller 512 controls switch 504to couple the downstream signal to a downstream amplifier 506, which maythen amplify the signal in the analog domain. The downstream signal isthen sent to a switch 508. Modem/controller 512 controls switch 508 toconnect to the downstream path and couples the downstream signal in thedownstream direction towards subscriber 110.

In the upstream direction, modem/controller 512 controls switch 508 tocouple the upstream signal to an amplifier 510. Amplifier 510 thenamplifies the signal in the analog domain. Modem/controller 512 controlsswitch 508 to then couple the upstream signal to directional coupler502. Directional couple 502 then sends the upstream signal in theupstream direction towards FDX node 102.

In the above configuration, two different amplifiers and paths are usedto amplify the downstream signals and the upstream signals,respectively. This uses multiple amplifiers, but only two switches,which may simplify the switching logic. The upstream and downstreampaths are isolated by TDD in this example and do not use crosstalkcancelation or an analog to digital/digital to analog conversion.

FIG. 5B depicts an example of a FDX bi-directional switched amplifier104-3 according to some embodiments. In this embodiment, a singleamplifier is used and switches are controlled to couple the upstream anddownstream signals through different paths to the same amplifier 526.Parts of the downstream and the upstream paths may go through similarcomponents, such as switches and amplifier 526. However, the overallpath that is taken is different between the downstream path and theupstream path. That is, the downstream path is coupled through adifferent sequence of switches compared to the upstream path.

Modem/controller 532 controls switches 522, 524, 528, and 530 indifferent time slots in which subscribers 110 are in either transmitmode or receive mode. In one example, modem/controller 532 receives thedownstream signal may use the downstream signal to determine whensubscribers 110 are in transmit mode or receive mode. For example, whena downstream signal is received, modem/controller 532 receives a signalfrom directional coupler 520 and determines that this time slot is forsubscribers 110 that are in receive mode. Then, modem/controller 532controls switches 522, 524, 528, and 530 to couple the signal to thedownstream path. When the downstream signal is not received,modem/controller 532 controls switches 522, 524, 528, and 530 to couplethe signal to the upstream path.

In the downstream direction, a directional coupler 520 may couple thedownstream signal to a switch 522. Modem/controller 532 controls switch522 to couple the signal to switch 524. Then, modem/controller 532controls switch 524 to couple the signal to amplifier 526. Amplifier 526can then amplify the signal in the analog domain and couple the signalto switch 528. Modem/controller 532 controls switch 528 to couple thesignal to a switch 530, which then sends the signal downstream.

In the upstream direction, modem/controller 532 controls switch 530 tocouple the signal to switch 524. From switch 524, modem/controller 532controls switch 524 to couple the upstream signal to amplifier 526 foramplification. Then, modem/controller 532 controls switch 528 and switch522 to send the upstream signal to directional coupler 520.

Method Flows

FIG. 6 depicts a simplified flowchart 600 of a method for processingfull duplex signals according to some embodiments. At 602, FDX expander104 receives a downstream signal and an upstream signal in a samefrequency band. As discussed above, in some embodiments, the downstreamsignal and the upstream signal may be received at the same time. Inother embodiments, the downstream signal and the upstream signal may bereceived at different times.

At 604, FDX expander 104 separates the downstream signal and theupstream signal into separate paths. As described above, different typesof FDX expanders 104 may separate the downstream signal and the upstreamsignal differently.

At 606, FDX expander 104 amplifies the downstream signal using a firstpath and amplifies the upstream signal using a second path. In someexamples, different amplifiers may be used to amplify the downstreamsignal and the upstream signal. However, a same amplifier may be used toamplify the downstream signal and the upstream signal, but differentpaths may be used to couple the downstream signal and the upstreamsignal to the amplifier.

At 608, FDX expander 104 sends the downstream signal to a subscriberdevice and sends the upstream signal to a FDX node 102. It will beunderstood that sending a downstream signal toward a subscriber devicemay send the signal through other FDX expanders 104, taps 112, or othernetwork devices. Additionally, sending the upstream signal toward FDXnode 102 may send the upstream signal to other FDX expanders 104.

Accordingly, FDX expanders 104 provide amplification in a full duplexnetwork without having to convert each amplifier to a FDX node 102. Thisallows the network to use amplification without converting the networkto an N+0 network. FDX expanders 104 isolate the upstream and downstreamsignals using different techniques. For example, crosstalk cancellationlogic may be used and/or a TDD mode.

System

FIG. 7 illustrates an example of a special purpose computer systems 700configured with a FDX expander 104 according to one embodiment. Computersystem 700 includes a bus 702, network interface 704, a computerprocessor 706, a memory 708, a storage device 710, and a display 712.

Bus 702 may be a communication mechanism for communicating information.Computer processor 706 may execute computer programs stored in memory708 or storage device 708. Any suitable programming language can be usedto implement the routines of some embodiments including C, C++, Java,assembly language, etc. Different programming techniques can be employedsuch as procedural or object oriented. The routines can execute on asingle computer system 700 or multiple computer systems 700. Further,multiple computer processors 706 may be used.

Memory 708 may store instructions, such as source code or binary code,for performing the techniques described above. Memory 708 may also beused for storing variables or other intermediate information duringexecution of instructions to be executed by processor 706. Examples ofmemory 708 include random access memory (RAM), read only memory (ROM),or both.

Storage device 710 may also store instructions, such as source code orbinary code, for performing the techniques described above. Storagedevice 710 may additionally store data used and manipulated by computerprocessor 706. For example, storage device 710 may be a database that isaccessed by computer system 700. Other examples of storage device 710include random access memory (RAM), read only memory (ROM), a harddrive, a magnetic disk, an optical disk, a CD-ROM, a DVD, a flashmemory, a USB memory card, or any other medium from which a computer canread.

Memory 708 or storage device 710 may be an example of a non-transitorycomputer-readable storage medium for use by or in connection withcomputer system 700. The non-transitory computer-readable storage mediumcontains instructions for controlling a computer system 700 to beconfigured to perform functions described by some embodiments. Theinstructions, when executed by one or more computer processors 706, maybe configured to perform that which is described in some embodiments.

Computer system 700 includes a display 712 for displaying information toa computer user. Display 712 may display a user interface used by a userto interact with computer system 700.

Computer system 700 also includes a network interface 704 to providedata communication connection over a network, such as a local areanetwork (LAN) or wide area network (WAN). Wireless networks may also beused. In any such implementation, network interface 704 sends andreceives electrical, electromagnetic, or optical signals that carrydigital data streams representing various types of information.

Computer system 700 can send and receive information through networkinterface 704 across a network 714, which may be an Intranet or theInternet. Computer system 700 may interact with other computer systems700 through network 714. In some examples, client-server communicationsoccur through network 714. Also, implementations of some embodiments maybe distributed across computer systems 700 through network 714.

Some embodiments may be implemented in a non-transitorycomputer-readable storage medium for use by or in connection with theinstruction execution system, apparatus, system, or machine. Thecomputer-readable storage medium contains instructions for controlling acomputer system to perform a method described by some embodiments. Thecomputer system may include one or more computing devices. Theinstructions, when executed by one or more computer processors, may beconfigured to perform that which is described in some embodiments.

As used in the description herein and throughout the claims that follow,“a”, “an”, and “the” includes plural references unless the contextclearly dictates otherwise. Also, as used in the description herein andthroughout the claims that follow, the meaning of “in” includes “in” and“on” unless the context clearly dictates otherwise.

The above description illustrates various embodiments along withexamples of how aspects of some embodiments may be implemented. Theabove examples and embodiments should not be deemed to be the onlyembodiments, and are presented to illustrate the flexibility andadvantages of some embodiments as defined by the following claims. Basedon the above disclosure and the following claims, other arrangements,embodiments, implementations and equivalents may be employed withoutdeparting from the scope hereof as defined by the claims.

1-20. (canceled)
 21. A method for full duplex communication includingsimultaneous transmission of upstream and downstream signals in a samefrequency band at a position in a network following a full duplex (FDX)DOCSIS node in a downstream direction, the method comprising: receivingat the position following the FDX node in the downstream direction, by acomputing device, a downstream analog signal from the FDX node and anupstream analog signal in the same frequency band; separating thedownstream analog signal and the upstream signal into a first path inthe computing device and a second path in the computing device, andamplifying each of the upstream signal in the first path and thedownstream signal in the second path; canceling crosstalk between theupstream and downstream signals so as to isolate the separateddownstream analog signal and the separated upstream analog signal fromone another in the computing device; sending, by the computing device,the amplified downstream analog signal downstream towards a subscriberdevice; and sending, by the computing device, the amplified upstreamanalog signal towards a full duplex node.
 22. The method of claim 21,wherein the downstream signal and the upstream signal are receivedduring a same time slot.
 23. The method of claim 22, wherein thesubscriber device is in a receive mode and another subscriber devicethat sent the upstream signal is in a transmit mode in the same timeslot.
 24. The method of claim 21, wherein the downstream signal and theupstream signal are received in different time slots.
 25. The method ofclaim 24, wherein the subscriber device is in a receive mode in a firsttime slot in the different time slots and another subscriber device thatsent the upstream signal is in a transmit mode in a second time slot inthe different time slots.
 26. The method of claim 21, cancelingcrosstalk between the downstream signal and the upstream signal isperformed in the computing device.
 27. The method of claim 21, whereinisolation of the downstream signal and the upstream signal comprises:converting the downstream signal or the upstream signal from analog todigital; and converting the downstream signal or the upstream signalfrom digital to analog.
 28. The method of claim 27, wherein amplifyingthe downstream signal or the upstream signal comprises performing one ormore of amplifying the downstream signal or the upstream signal beforeconverting the downstream signal or the upstream signal from analog todigital and amplifying the downstream signal or the upstream signalafter converting the downstream signal or the upstream signal fromdigital to analog.
 29. The method of claim 27, wherein converting thedownstream signal or the upstream signal from analog to digital and fromdigital to analog isolates a receiver side that receives the downstreamsignal or the upstream signal and a transmitter side that transmits thedownstream signal or the upstream signal.
 30. The method of claim 27,further comprising: decoding the downstream signal or the upstreamsignal after converting the downstream signal or the upstream signalfrom analog to digital; and reconstructing the downstream signal or theupstream signal after decoding.
 31. The method of claim 27, whereinisolation of the downstream signal and the upstream signal comprisescanceling crosstalk from either the downstream signal and the upstreamsignal after converting the downstream signal or the upstream signalfrom analog to digital.
 32. The method of claim 27, wherein isolation ofthe downstream signal and the upstream signal comprises cancelingcrosstalk from either the downstream signal and the upstream signalbefore converting the downstream signal or the upstream signal fromanalog to digital.
 33. The method of claim 21, wherein amplifying thedownstream signal using the first path and the upstream signal using thesecond path comprises: coupling the downstream signal to a firstamplifier to amplify the downstream signal during a first time slot; andcoupling the upstream signal to a second amplifier to amplify theupstream signal during a second time slot.
 34. The method of claim 21,wherein amplifying the downstream signal using the first path and theupstream signal using the second path comprises: coupling the downstreamsignal to an amplifier to amplify the downstream signal during a firsttime slot; and coupling the upstream signal to the amplifier to amplifythe upstream signal during a second time slot.
 35. A system comprising:one or more directional couplers configured to receive a downstreamanalog signal and an upstream analog signal in a same frequency band andcouple the downstream signal in a first path and couple the upstreamsignal in a second path; one or more amplifiers configured to amplifythe analog downstream signal using the first path and the upstreamanalog signal using the second path; and one or more processorsconfigured to cancel crosstalk between the downstream signal and theupstream signal, and to isolate the downstream signal and the upstreamsignal from one another, wherein the one or more directional couplersare configured to send the amplified downstream analog signal downstreamtowards a subscriber device and send the amplified upstream analogsignal towards a full duplex node.
 36. The apparatus of claim 35,further comprising: a first analog to digital converter configured toconvert the downstream signal or the upstream signal from analog todigital; and a second analog to digital converter configured to convertthe downstream signal or the upstream signal from digital to analog. 37.The apparatus of claim 36, wherein the isolation logic is configured tocancel crosstalk from either the downstream signal and the upstreamsignal after the first analog to digital converter converts thedownstream signal or the upstream signal from analog to digital.
 38. Theapparatus of claim 35, further comprising: a first amplifier to amplifythe downstream signal during a first time slot; and a second amplifierto amplify the upstream signal during a second time slot.
 39. Theapparatus of claim 35, further comprising an amplifier to amplify thedownstream signal during a first time slot and amplify the upstreamsignal during a second time slot.